Widgetize Google Gadjets plugin
I installed this plugin and found that there is some kind of conflict (maybe with jquery??). When I add the embedded code in the widget, and saved it, the sidebar had parts of the Commons dropdown options from the header on the sidebar rather than content from the gadget. This happened with three gadgets I tried.
The following shows the sidebar of a test blog with the American Memories collection gadget from Library of Congress: http://testprivategroup.commons.gc.cuny.edu/